In automation systems for engineering or industrial plants, e.g. in the process industry, production and manufacturing industry, building services technology or network technology, locally distributed, decentralized field devices (process devices) perform prescribed functions in the plants concerned, as part of the plant automation, and in doing so exchange process, plant and/or device-related data, between one another when necessary but always with higher-level components of the automation system, in particular its management or engineering system. Field devices include, among other things, transducers for pressure, temperature, flow volume, occupancy level etc., analytical devices for gas or fluid analysis, weighing systems, setting drives, position regulators for valves, other local regulators, and frequency converters for electromotive drives. For the purpose of exchanging data within the automation system, the field devices in the local peripheral area, together with any local controller and regulator, operating and monitoring facilities, are linked with each other via field buses or other communication paths, wherein different field buses are linked with each other via bus couplers. The field buses can in turn be linked via control devices, such as for example programmable logic controllers, into a central plant bus to which is also connected the management or engineering system, that is the central controller, regulator, operating and monitoring facilities.
Field devices generally have adjustable device parameters such as for example limit values for alarms or warnings, calibration curves, parameters in evaluation algorithms for signal processing etc. The device parameters can be set and modified in different ways depending on the device type and manufacturer, e.g. via input facilities such as a keyboard, directly on the field device and/or by means of special software programs which are installed on a host computer and communicate with the field device via the latter's communication interface. To an increasing extent, separate operating devices are used for the local operation of the field device, for example so-called handheld PCs, which preferably communicate with the field device wirelessly. When they are input or modified, the device parameters are visualized by means of the display facilities on the operating device and/or the field device, where the display facilities can generally also be used to display further process, device and plant data, such as for example process values. Using an operating device it is also possible to operate several field devices, including those of different types or from different manufacturers.